Bennhold's Congo Red
for Amyloid

Solutions

Ethanol, 80%
Mayer's hemalum
Congo red
Congo red 1 g
Distilled water 100 mL
Lithium carbonate
Lithium carbonate as required
Distilled water 100 mL
Dissolve to saturation.

Tissue sample
Paraffin sections of formalin fixed tissues are satisfactory.

Method

  1. Bring sections to water via xylene and ethanol.
  2. Place into the congo red solution for
    a) 30 minutes at room temperature, or
    b) 45 minutes at 56°C, or
    c) 15 seconds at boiling.
  3. Drain and, without rinsing, place into lithium carbonate solution for 15 seconds.
  4. Drain and, without rinsing, differentiate in 80% ethanol.
    This usually takes just a few seconds.
  5. Wash well with tap water.
  6. Stain nuclei with hematoxylin and blue.
  7. Dehydrate with ethanol.
  8. Clear with xylene and mount with a resinous medium.

Expected results

Notes

  1. Amyloid displays apple green birefringence when viewed with crossed polarisers, one above and one below the section.
  2. The congo red is most commonly applied for 30 minutes at room temperature.
  3. Differentiation in 80% ethanol is difficult to control, and amyloid is often poorly demonstrated. Due to this the method is not usually recommended.

 

Reference
Bennhold, H., (1922),
Eine specifische amyloidfärbung mit kongorot,
Münchener Medizinische Wochenschrift, v 44, page 1537

 


 

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